1. Field of the Invention
The present invention generally relates to a camera with an electronic flash, and more particularly to charge control technics of an electronic flash which is built in or connected to a silver halide camera, a digital camera or the like.
2. Description of Related Art
In recent years, in a silver halide camera or an electronic still camera with a built-in electronic flash, the electronic flash and camera controlling circuits (a CCD driving circuit, an LCD driving circuit and so on) share the same power source. A load is large at the beginning of the charge of the electronic flash, and thus not enough electricity for normally operating the camera controlling circuits can be supplied to the camera controlling circuits. Therefore, the camera controlling circuits is not operated during the charge, and the charge is suspended when the camera controlling circuits is operated (Japanese Patent No. 2521128).
In the case of the above-described camera, however, the camera controlling circuits start to be operated after a main capacitor of the electronic flash is fully charged, and thus a shooting is not possible until the electronic flash is fully charged and a liquid crystal display (LCD) gets ready for displaying an image and a CCD gets ready for imaging the image. As a result, a good opportunity for shooting can be missed.
Japanese Patent Provisional Publication No. 10-80069 discloses a camera which detects that the voltage of a main capacitor reaches a light-emission-possible voltage and gets ready for a shooting before the main capacitor is fully charged. In case of an electronic still camera that gets ready for a shooting after an LCD displays an image, the image is not displayed on the LCD until an electronic flash is fully charged since a relatively large current is sent for driving the LCD. Therefore, likewise the above-described camera, the electronic still camera takes a long time to get ready for a shooting, and a good opportunity for shooting can be missed as a result.
On the other hand, an imaging device with an electronic flash disclosed in Japanese Patent Provisional Publication No. 6-205277 stops the charge when the charging voltage reaches a light-emission-possible voltage to display an image on an LCD. Thus, the shooting is ready in a short time, but a guide number declines and a light-emission-possible time is short.
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of a camera with an electronic flash which can perform a shooting as soon as a charging voltage reaches a light-emission-possible voltage.
To achieve the above-described object, the present invention is directed to a camera with an electronic flash comprising: the electronic flash that has a charging circuit that charges a main capacitor and a light-emitting part that emits a light by discharging electricity accumulated in the main capacitor; a power source part that supplies electricity to the charging circuit and camera circuits other than the electronic flash; a charging voltage determining device that determines a charging voltage of the main capacitor; and a controlling part that stops functions of the camera circuits and charges the electronic flash by a first charging current from the start of the charge until the charging voltage reaches a light-emission-possible voltage that is lower than a full-charge voltage, and switches the first charging current to a second charging current that is lower than the first charging current to continue the charge and allows operations of the camera circuits to get ready for a shooting when the charging voltage reaches the light-emission-possible voltage.
According to the present invention, the electronic flash and the camera circuits share the power source part, and the controlling part controls the charge of the main capacitor and the operation of the camera circuits so that the camera gets ready for the shooting in a short time. When the charge is started, the controlling part stops the functions of the camera circuits and rapidly charges the electronic flash by a high electric current (the first charging current). When the charging voltage reaches a shooting-possible voltage (the light-emission-possible voltage) that is lower than the full-charge voltage, the controlling part switches the first charging current to the second charging current that is lower than the first charging current to continue the charge and the camera gets ready for the shooting.
Therefore, the shooting gets ready as soon as the charging voltage reaches the light-emission-possible voltage. A preparation time from the start of the charge to the time at which the camera gets ready for the shooting is short compared with that in a conventional camera that starts to activate the camera circuits after the full charge. Moreover, a decline of the performance of the electronic flash such as a decline of a guide number and a reduction of a light-emission-possible time can be prevented since the charge is continued by the second charging current after the charging voltage reaches the light-emission-possible voltage.
To achieve the above-described object, the present invention is directed to a camera with an electronic flash comprising: the electronic flash that has a charging circuit that charges a main capacitor and a light-emitting part that emits a light by discharging electricity accumulated in the main capacitor; a power source part that supplies electricity to the charging circuit and camera circuits other than the electronic flash; a charging voltage determining device that determines a charging voltage of the main capacitor; and a controlling part that stops functions of the camera circuits and charges the electronic flash by a first charging current from the start of the charge until the charging voltage reaches a preset voltage that is a predetermined voltage lower than a light-emission-possible voltage that is lower than a full-charge voltage, and switches the first charging current to a second charging current that is lower than the first charging current to continue the charge and activates the camera circuits when the charging voltage reaches the preset voltage.
According to the present invention, when the charge is started, the controlling part stops the functions of the camera circuits and rapidly charges the electronic flash by a high electric current (the first charging current). When the charging voltage reaches the preset voltage that is the predetermined voltage lower than a shooting-possible voltage (the light-emission-possible voltage), the controlling part switches the first charging current to the second charging current that is lower than the first charging current to continue the charge and starts to activate the camera circuits at the same time. The camera circuits are activated so that the camera gets ready for the shooting as soon as the charging circuit reaches the light-emission-possible voltage.
A preparation time from the start of the charge to the time at which the camera gets ready for the shooting is short compared with that in the conventional camera. Moreover, a decline of the performance of the electronic flash can be prevented since the charge is continued by the second charging current after the charging voltage reaches the light-emission-possible voltage.
The camera may further comprise a maximum electricity determining device that determines electricity that can be supplied from the power source part and an automatic setting device that changes at least one of the following, the preset voltage, the first charging current and the second charging current, according to the determination result of the maximum electricity determining device.
The present invention may be applied to a camera, such as an electronic still camera with a liquid crystal monitor, whose camera circuits include an imaging device, a signal processing circuit that processes signals outputted from the imaging device to generate image data and an image displaying device that displays an image according to the image data.